1. Field of the Invention
The present invention is generally in the field of electronic circuits and systems. More specifically, the present invention is in the field of communications circuits and systems.
2. Background Art
In the field of wireless communications, 60 GHz technology pursues very high throughput in short-range wireless data transmissions making possible, for example, high-speed communication between multiple wireless devices associated to one another in a communications network. To enable this inherent high-speed communication, each wireless device, or station (STA), within a network must associate itself with a personal basic service set, or PBSS, which is essentially a set of all devices, or stations, that are associated with each other, and thus, can communicate with one another. Within a PBSS, a personal basic service set control point, or PCP, is the device that essentially controls the timing of communications between all devices associated to a particular PBSS.
In order for one wireless STA to associate itself with another wireless STA or PCP, the wireless STA must actively or passively scan for the presence of the other wireless STA or PCP. When a wireless STA is not yet associated to a PCP, i.e., is not part of any PBSS, the wireless STA may perform an active or passive scan any time without hindrance because the wireless STA need not listen for any transmissions from any PCP, nor are any data transmissions scheduled to be sent to or from the wireless STA.
However, if a wireless STA is already associated with a PCP, i.e. is already part of a PBSS and is looking to join another PBSS or PCP/STA not belonging to the associated PBSS, the requisite active or passive scan may be difficult to implement because the associated PCP can schedule data transmissions at any time. If the PCP schedules and transmits data to or from the STA during the active scan, the wireless STA must abort the scan process or suffer the loss of the transmitted data. FIG. 1 shows an exemplary timing diagram representative of data transmission from a PCP during a conventional active scan by an associated wireless STA. FIG. 1 shows a plurality of fixed-length beacon intervals 102, fixed-length time periods during which data transmissions may be scheduled between high-speed devices, shown as the space between two adjacent upward pointing arrows. These beacon intervals (BI) are typically 100 ms in duration. However, one of ordinary skill in the art would appreciate that BI duration may be longer or shorter than this value.
According to this conventional approach, an associated wireless STA may begin an active scan 110 lasting, for example, 2 BI. Each active scan 110 of a particular wireless channel may be separated by an interval 120, during which the associated wireless STA does not perform an active scan. According to the WGA standard, the wireless STA is also typically required to listen for data 130, which may include beacons and/or management frames, for example, from the associated PCP/peer STA each BI. Because some of the data 130 transmitted by an associated PCP/peer STA occurs during a scan interval 110, the data transmitted during those beacons 130 is lost to the wireless STA. Thus, because the wireless STA requires an undisturbed, continuous time period to perform the active scan, it can be very difficult for an already associated wireless STA to perform the active scan without losing concurrently transmitted data. Passive scanning poses similar challenges to active scanning, since a wireless STA must silently scan for beacon transmissions on different channels from neighboring PBSSs, just as during an active scan.
Consequently, there is a need to overcome the drawbacks and deficiencies in the art by providing a scan scheduling solution enabling a wireless device in an associated state to schedule and perform a scan while avoiding the loss of critical data transmitted during the scan.